The utility model relates to a reaction kettle for uniformly mixing a dropping material and a reaction backing material. The reaction kettle comprises a reaction kettle body, wherein the reaction kettle body comprises an upper cover and a bottom, and a stirring paddle is installed on the upper cover; one end of the stirring paddle is connected with a motor, and the other end of the stirring paddle extends into the kettle body; at least one dropping material barrel is arranged on the upper cover and is communicated with the inner part of the kettle body, and a valve is arranged at the communicated position; an external circulating pipeline is connected between the upper cover and the bottom; and two ends of the external circulating pipeline are communicated with the inner part of the kettle body. The dropping material is put in the dropping material barrel. When start to drip, an external circulating pump is opened, the reaction backing material flows out from the bottom of the reaction kettle, passes through the external circulating pipeline and the external circulating pump, flows into the reaction kettle from the top of the reaction kettle, so that the reaction backing material is fully mixed with the dropping material under the combined action of the internal circulation formed by the stirring paddle and the external circulation formed by an external circulating system. Thus, the molecular weight of a synthetic product is more uniform, and the performance of the product is greatly increased.